This invention relates to a control signal generator for the commutating device of a brushless electronics motor in general and move particularly an improved control signal generator permitting a digital drive of the motor.
A control signal generator comprising two Hall effect generators, which are shifted relative to each other by 90.degree. electrically and magnetically and furnish Hall signals depending on the rotor position, and a gating circuit which derives control signals for the switching elements of the commutating device, from the Hall signals of the Hall effect generators is known from "VDE-Fachberichte" No. 25, 1968, pages 147 to 151, in particular FIG. 7. This control signal generator is used in an electronic motor whose stator winding consists of four individual windings, lying in pairs in winding slots of a coil core and disposed at right angles to each other. The stator winding encloses a two-pole rotor magnet. Two magnetic field sensitive components, i.e. two Hall effect generators, which are stationarily disposed, but shifted spatically by 90.degree. relative to each other, are provided as rotor position indicators to signal the position of the rotor magnet. Each Hall effect generator is disposed under a pair of individual windings. This involves a so-called "0.degree. shift". The two Hall effect generators are driven by the magnetic field of the revolving rotor so that the two Hall signals of the one change sinusodially with the angle of rotation and those of the other as a cosine. A gating circuit (FIG. 9 of the same reference) derives control or switching signals for the commutating device from the four Hall signals of the two Hall effect generators. They are derived from the intersections of the Hall signals. The commutating device is equipped with four power transistors as switching elements, connected in series to the individual windings. Each power transistor is preceded by a series transistor. Because all emitter currents of the series transistors flow through one common series resistor, the effect of the control by the two Hall effect generators is such that only the one power transistor whose associated series transistor receives the highest magnitude Hall signal carries current. The series transistors control the power transistors which, in turn, control the currents in the individual windings. This involves an analog drive in which it is quite possible for two single windings in transitory positions to be current carrying simultaneously.
A similar control signal generator for an electronics motor is also known from "Siemens-Zietschrift", April 1971, pages 206 to 208, in particular FIGS. 2 and 5. The stator winding therein also has four individual windings. There, too, two Hall effect generators spatially shifted 90.degree. relative to each other are used. However, they are now not disposed axially to the individual windings, but at half the angle between the individual windings of the stator winding. This involves a so-called "45.degree. shift". The control signals for the commutating device are derived by means of the gating circuit, not from the intersections, but from the zero crossings of the Hall signals generated by the rotor flux. This involves driving the electronics motor digitally. Only H and L signals are used so that each individual winding becomes inactive when the next individual winding is connected.